In the weeks leading up to the start of the 2008 season, controversy swirled around the Nittany Lions' starting quarterback position. Daryll Clark, the more experienced and agile quarterback was being weighed against the younger, more prolific passing threat in Devlin. In the end, Penn State coach Joe Paterno chose to start Daryll Clark while having him split as much time with Devlin as would be possible. Lopsided victories in the first four games of the 2008 season provided Devlin with much playing time. In games against Coastal Carolina, Oregon State, Syracuse, and Temple, Devlin threw for 260 yards and was 18 of 35. When Clark was forced out in the fourth quarter of the Nittany Lions' crucial game versus Ohio State due to a concussion, Devlin led the team on a go-ahead drive that was culminated by his own 1-yard touchdown run. He also had some playing time against Wisconsin, Michigan, Indiana, and Michigan State. Devlin appeared in ten games for the Nittany Lions, passing for 459 yards, four touchdowns and no interceptions.
Devlin led the 2009 squad to a 6–5 record. Devlin started all eleven games for the Blue Hens, passing for 2,664 yards, sixteen touchdowns, and nine interceptions. In the final game of the season against Villanova University, Devlin passed for Delaware school records in completions (42) and attempts (58) and threw for 407 yards. Devlin was named the Colonial Athletic Association Football Offensive Player of the Week twice during the season, and led the league in passing average per game (242.2 yards) and total offense per game (253.7 yards). He also was honored as the Eastern College Athletic Conference Division I – Championship Subdivision Offensive Player of the Week. The Sports Network wrote that "Devlin has put some teeth back into the Blue Hen passing attack with his accurate throws and on-field leadership", and included him as a finalist in the voting for the 2009 Walter Payton Award, given to the most outstanding offensive player in the Division I Football Championship Subdivision (formerly Division I-AA). In November 2009, Devlin was honored as the local College Player of the Year by the Eagles Fly for Leukemia program, an organization supporting pediatric cancer and leukemia research in the Delaware Valley.
In June, Devlin was selected to the Consensus Draft Services Pre-Season NCAA Division I Football Championship Subdivision pre-season honorable mention All-American. The team is made up of players at the FCS level who the CDS staff predicts will be among the top players in the nation and have a chance to be selected in the National Football League Draft in April 2011. In July, Devlin was placed on the watchlists for the Walter Payton Award and the Johnny Unitas Golden Arm Award.
In the season's first game against West Chester, Devlin completed 14 of 23 passes for 163 yards with three touchdown passes to lead the team to a 31-0 shutout. Although Devlin fractured a bone in his non-throwing wrist in the first quarter of the game against South Dakota State, he played through the middle of the fourth quarter. Although cleared to play the following week against Duquesne, Devlin stood on the sidelines. Devlin came back the following week with a big second-half win against Richmond, but was knocked out of the following week's game against James Madison with a concussion. Back at home against Maine, Devlin completed 20 of 36 passes for 286 yards, leading the Blue Hens to their sixth win of the season. After a close win against Rhode Island and a one-point loss against William & Mary, he dominated against Towson, completing 29 of 38 passes for 318 yards and one touchdown while running for another score. Devlin became the ninth Delaware player to pass for over 4,000 yards in a career.
Devlin entered the 2011 NFL Draft and was regarded as one of the top ten quarterbacks entering the draft by NFL Network analyst Mike Mayock, but was not drafted. He was targeted as the first overall pick in the 2011 UFL Draft, but declined to sign a mandatory contract.
Devlin was signed to the Cleveland Browns on August 27, 2015. He was released by the Browns on September 5, 2015. On December 31, 2015 Devlin was re-signed by the Cleveland Browns to be back-up to Austin Davis after it was determined Johnny Manziel would not play due to his status in the NFL concussion protocol.
^Schefter, Adam (May 3, 2011). "Twitter: Adam Schefter (verified account)". Retrieved May 3, 2011. Delaware QB Pat Devlin was targeted as No. 1 selection in UFL Draft, but was required to sign a contract prior to draft. He chose not to.